Lethal-7 is down-regulated by the hepatitis B virus x protein and targets signal transducer and activator of transcription 3.

Published

Journal Article

BACKGROUND & AIMS: The pleiotropic hepatitis B virus (HBV) x protein (HBx), associated with hepatocellular carcinoma (HCC), has been implicated in the deregulation of cellular gene expression at the transcriptional level. To date, it remains unknown if HBx regulates the expression of miRNAs which play important roles in gene-regulation at the post-transcriptional and/or translational level. METHODS: miRNA microarrays were employed to compare the expression of cellular miRNAs in HBx-versus control-HepG2 cells. Reverse-transcription Taqman realtime-PCR was used to examine let-7a expression in normal liver as well as paired HCC-tumor and adjacent non-tumorous liver. Let-7a miRNA was functionally characterized in cells with transiently altered let-7a expression. The direct target of let-7a was identified in silico and validated using 3'UTR-reporter assay. RESULTS: HBx up-regulates 7 and down-regulates 11 miRNAs, including the let-7 family. HBx expression was found to have a significant inverse correlation with the expression of the highly-expressed members of the let-7 family in HCC patients, highlighting the clinical relevance of our observations. Further characterization of let-7a, the most highly expressed let-7 family member, revealed that it negatively regulates cellular proliferation partly through targeting signal transducer and activator of transcription 3 (STAT3). HBx-mediated down-regulation of let-7a and up-regulation of STAT3 supports cell proliferation in HBx cells. CONCLUSION: This study thus represents the first demonstration of HBx's ability to deregulate cellular miRNA expression. The deregulation of the expression of the let-7 family of miRNAs by HBx may represent a potential novel pathway through which HBx acts to deregulate cell proliferation leading to hepatocarcinogenesis.

Full Text

Cited Authors

  • Wang, Y; Lu, Y; Toh, ST; Sung, W-K; Tan, P; Chow, P; Chung, AYF; Jooi, LLP; Lee, CGL

Published Date

  • July 2010

Published In

Volume / Issue

  • 53 / 1

Start / End Page

  • 57 - 66

PubMed ID

  • 20447714

Pubmed Central ID

  • 20447714

Electronic International Standard Serial Number (EISSN)

  • 1600-0641

International Standard Serial Number (ISSN)

  • 0168-8278

Digital Object Identifier (DOI)

  • 10.1016/j.jhep.2009.12.043

Language

  • eng